Method for manufacturing a microelectromechanical structure and microelectromechanical structure

Abstract

A method for manufacturing a microelectromechanical structure. The method includes: forming a first and a second functional layer including recesses, a third functional layer, and three insulating layers situated therebetween, a structured lateral area of the third functional layer defining a movable structure, the insulating layers and the first and second functional layers each including a lateral area situated beneath the structured lateral area of the third functional layer and corresponding to a perpendicular projection of the structured lateral area; etching the insulating layers to remove the lateral area of the third insulating layer, and expose the movable structure, all recesses of the first functional layer situated in the lateral area of the first functional layer being formed by narrow trenches, the first functional layer being formed to include an electrically insulated segment in the lateral area which is separated from the remainder of the first functional layer by trenches.

What is claimed is: 
     
       1. A method for manufacturing a microelectromechanical structure, the method comprising:
 forming at least one first insulating layer above a substrate; 
 forming a first functional layer on the first insulating layer the first functional layer being provided with recesses which extend across an entire thickness of the first functional layer; 
 forming a second insulating layer on the first functional layer; 
 forming a second functional layer above the second insulating layer, the second functional layer being provided with recesses which extend across an entire thickness of the second functional layer; 
 forming a third insulating layer above the second functional layer; 
 forming a third functional layer on the third insulating layer, a lateral area of the third functional layer being structured by recesses in such a way that a structured lateral area defines a movable structure, the first, second, and third insulating layers and the first and second functional layers each including a lateral area, which is situated beneath the structured lateral area of the third functional layer and corresponds to a perpendicular projection of the structured lateral area; and 
 etching the first, second, and third insulating layers, the third insulating layer being completely removed in the lateral area of the third insulating layer, and the movable structure being exposed by the removal of the third insulating layer in the lateral area, the second insulating layer being at least partially removed in the lateral area, and the third insulating layer being at least partially removed in the lateral area; 
 wherein all recesses of the first functional layer which are situated in the lateral area of first functional layer are formed by narrow trenches whose width is smaller than twice a perpendicular distance between the first and third functional layers, and 
 wherein the first functional layer is formed in such a way that it includes at least one electrically insulated segment in the lateral area, which is separated from a remainder of the first functional layer by trenches. 
 
     
     
       2. The method as recited in  claim 1 , wherein a width of the trenches in the lateral area of the first functional layer is greater than half a thickness of the first functional layer. 
     
     
       3. The method as recited in  claim 1 , wherein the second functional layer is formed in such a way that it includes at least one first segment and one second segment, and the first and second segments are electrically insulated from one another, the first functional layer being formed in such a way that it includes a first electrically insulated segment and a second electrically insulated segment which are separated from one another and from a remainder of the functional layer by trenches, the first electrically insulated segment of the first functional layer being situated beneath the first segment of the second functional layer, and the second electrically insulated segment of the first functional layer being situated beneath the second segment of the second functional layer. 
     
     
       4. The method as recited in  claim 1 , wherein the first functional layer is formed in such a way that it includes a shielding segment in the lateral area, which is separated from a remainder of the first functional layer by trenches, the shielding segment being situated beneath a recess of the second functional layer and conductively connected to at least one segment of the second functional layer. 
     
     
       5. The method as recited in  claim 1 , wherein the first functional layer is formed in such a way that it includes a first and a second shielding segment in the lateral area, which are situated in surroundings beneath a recess of the second functional layer, the first shielding segment being conductively connected to a first segment of the second functional layer, and the second shielding segment being conductively connected to a second segment of the second functional layer. 
     
     
       6. The method as recited in  claim 1 , wherein the recesses in the second functional layer are formed by the following substeps:
 forming trenches in the second functional layer, which extend across the entire thickness of the second functional layer, the trenches subsequently being filled through the formation of a first auxiliary layer; 
 forming etching accesses in the first auxiliary layer, which partially expose the second functional layer, subareas of the second functional layer being removed as a result of subsequent etching, and the etching accesses being closed by the third insulating layer prior to formation of the third functional layer, the first auxiliary layer being at least partially removed during the etching of the third insulating layer. 
 
     
     
       7. The method as recited in  claim 3 , wherein subareas of the first insulating layer and of the second insulating layer are removed during etching in such a way that a remaining subarea of the first insulating layer forms a base structure for the first insulated segment of the first functional layer, and a remaining subarea of the second insulating layer forms a base structure for a segment of the second functional layer. 
     
     
       8. The method as recited in  claim 1 , wherein at least one strip conductor is formed by the first functional layer and/or at least one detection electrode is formed by the third functional layer. 
     
     
       9. A microelectromechanical structure, comprising:
 a substrate; and 
 a first, second, and third functional layer, the third functional layer including a structured lateral area which forms a movable structure, the first and second functional layers each including a lateral area, which is situated beneath the structured lateral area of the third functional layer and corresponds to a perpendicular projection of the structured lateral area; 
 wherein all recesses of the first functional layer which are situated in the lateral area of the first functional layer are formed by narrow trenches whose width is smaller than twice a perpendicular distance between the first and third functional layers, the first functional layer in the lateral area including at least one electrically insulated segment which is separated from a remainder of the first functional layer by trenches. 
 
     
     
       10. The microelectromechanical structure as recited in  claim 9 , wherein the second functional layer includes at least one first and one second segment, and the first and second segments are electrically insulated from one another, the first functional layer includes a first and a second electrically insulated segment, which are separated from one another and from a remainder of the functional layer by trenches, the first electrically insulated segment of the first functional layer being situated beneath the first segment of the second functional layer, and the second electrically insulated segment of the first functional layer being situated beneath the second segment of the second functional layer.